Mucosa-associated Lymphoid Tissue (MALT) Lymphoma

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Mucosa-associated Lymphoid Tissue (MALT) Lymphoma

In this article

The body's immune system is made up of a number of masses of lymphoid tissue or organs, as well as circulating leukocytes that originate from the bone marrow. The main lymphoid organs are:

Bone marrow, thymus, tonsils, spleen and lymph nodes

Mucosa-associated lymphoid tissue (MALT)

Gut-associated lymphoid tissue (GALT)

Bronchus-associated lymphoid tissue (BALT)

Skin-associated lymphoid tissue (SALT)

Definition

MALT lymphoma is a subtype of non-Hodgkin's lymphoma with it's own specific pathology, histology and clinical features.[1] It is distinct because it involves lymphoid proliferation in mucosa-associated lymphoid tissue (MALT) rather than lymph nodes.

MALT lymphomas follow a different course to nodal B-cell lymphomas. They tend to remain localised for longer, lack poor prognostic features and have a higher five-year survival rate. MALT lymphomas can be divided into:

Gastric: the most common type and associated with Helicobacter pylori infection.

Non-gastric: most often in the head and neck, lung and eye. Non-gastric MALT lymphomas are not associated with H. pylori infection.

Aetiology

MALT can develop in nearly every organ as a result of chronic infection or an autoimmune process. If there is prolonged lymphoid proliferation, a malignant clone can emerge and a MALT lymphoma could follow.

Investigations

Barium contrast studies of the upper and lower gastrointestinal tract.

CT scan and MRI scan.

Endoscopy.

Bone marrow aspiration.

Management

Management is different for gastric and non-gastric MALT lymphomas.

Treatment with a proton pump inhibitor (PPI) and antibiotics to eradicate H. pylori is the main treatment for most gastric MALT lymphomas, which are often low-grade and remain localised for several years. Treatment with chemotherapy, surgery or radiotherapy has not been demonstrated to be superior to antibiotic treatment.

Rituximab alone or in combination with chemotherapy is reported to provide high response rates and has been advocated for those with disseminated or recurrent disease.[10]

Surgery has only a limited role in treatment. Surgery for non-gastrointestinal MALT lymphoma is usually restricted to excisional biopsies. Partial or total gastrectomy is associated with considerable morbidity and is rarely necessary.

Diagnosis: endoscopy and gastric biopsy. There are characteristic histological features.

Treatment:

Eradication of H. pylori with antibiotics and a PPI or H2-receptor antagonist can lead to a complete remission of gastric MALT lymphoma in between 65-70% of cases and is first-line treatment for early-stage disease.[1, 11]

If H. pylori status is negative, eradication treatment may not work.

Close follow-up using endoscopy is needed after eradication treatment to ensure a complete response.[12]

If there is locally-advanced or high-grade disease, chemotherapy, monoclonal antibody treatment with rituximab, or radiotherapy should be added to eradication treatment.

Surgery is reserved for refractory disease, as gastric preservation is preferred if possible.

Current clinical trials involving these different treatment modalities are underway.

Prognosis: the overall five-year survival and disease-free survival rates are as high as 90% and 75%, respectively.[13]70-80% of patients reveal complete remission of MALT lymphoma following successful eradication of H. pylori.[14]

Lung MALT lymphoma

Clinical features: arises from bronchus-associated lymphoid tissue (BALT). 40% are asymptomatic and present with a solitary pulmonary nodule on CXR.[1] There may be cough, dyspnoea, haemoptysis, fever, weight loss. Can spread throughout the lung and to other MALT.

Treatment: surgery (if localised), chemotherapy, radiotherapy.

Prognosis: usually has an indolent course, remaining localised to the lung for long periods before dissemination.[20]

Thyroid MALT lymphoma

Associated with: particularly associated with inflammatory conditions in the thyroid and salivary glands.[21]

Clinical features: thyroid mass, possible obstructive symptoms.

Diagnosis: may need open biopsy.

Treatment: surgery ± radiation for local disease; chemotherapy added if the disease is advanced.

Skin MALT lymphoma

Associated with: B. burgdorferi infection may be associated but this is not clear.[4]

Clinical features: presents as a few, multiple, pink, red-to-violaceous papules, plaques, or nodules that most often involve the trunk or extremities, especially the arms.[22]

; Most patients with minimal histological residuals of gastric MALT lymphoma after successful eradication of Helicobacter pylori can be safely managed by a watch-and-wait strategy. Experience from a large international series. Gut. 2007 Jul 16.

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